CA1175265A - Method for making holographic optical elements with high diffraction efficiencies - Google Patents
Method for making holographic optical elements with high diffraction efficienciesInfo
- Publication number
- CA1175265A CA1175265A CA000411879A CA411879A CA1175265A CA 1175265 A CA1175265 A CA 1175265A CA 000411879 A CA000411879 A CA 000411879A CA 411879 A CA411879 A CA 411879A CA 1175265 A CA1175265 A CA 1175265A
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- Canada
- Prior art keywords
- angle
- copy
- bragg
- thickness
- bragg surfaces
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 16
- 230000003287 optical effect Effects 0.000 title claims abstract description 16
- 230000003362 replicative effect Effects 0.000 claims abstract description 21
- 238000012545 processing Methods 0.000 claims abstract description 12
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 42
- 230000001427 coherent effect Effects 0.000 claims description 14
- 230000008859 change Effects 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000012544 monitoring process Methods 0.000 claims 2
- 239000000499 gel Substances 0.000 abstract description 7
- 229910052709 silver Inorganic materials 0.000 abstract description 6
- 239000004332 silver Substances 0.000 abstract description 6
- -1 silver halide Chemical class 0.000 abstract description 6
- 230000008961 swelling Effects 0.000 abstract description 4
- 108010025899 gelatin film Proteins 0.000 abstract description 3
- 108010010803 Gelatin Proteins 0.000 description 10
- 239000008273 gelatin Substances 0.000 description 10
- 229920000159 gelatin Polymers 0.000 description 10
- 235000019322 gelatine Nutrition 0.000 description 10
- 235000011852 gelatine desserts Nutrition 0.000 description 10
- 239000000839 emulsion Substances 0.000 description 5
- 239000000562 conjugate Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 2
- 230000002452 interceptive effect Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- NCGICGYLBXGBGN-UHFFFAOYSA-N 3-morpholin-4-yl-1-oxa-3-azonia-2-azanidacyclopent-3-en-5-imine;hydrochloride Chemical group Cl.[N-]1OC(=N)C=[N+]1N1CCOCC1 NCGICGYLBXGBGN-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
- G03H1/04—Processes or apparatus for producing holograms
- G03H1/20—Copying holograms by holographic, i.e. optical means
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/106—Scanning systems having diffraction gratings as scanning elements, e.g. holographic scanners
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Holo Graphy (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
METHOD FOR MAKING HOLOGRAPHIC OPTICAL
ELEMENTS WITH HIGH DIFFRACTION
EFFICIENCIES
Abstract Production quantities of a multi-element holographic scanner disc are made by optically replicating a silver halide master disc one element at a time in a dichromated gelatin film.
The dichromated gelatin film swells during pro-cessing. The swell is monitored during production by determining the shift in the angle of the Bragg surfaces within the gel. The angle of the repli-cating beam for each element is changed from that of the original reference beam to establish a Bragg angle at exposure which will be tilted to the pro-per angle after swelling in order to maximize the diffraction efficiency of the element at the original reference beam angle.
ELEMENTS WITH HIGH DIFFRACTION
EFFICIENCIES
Abstract Production quantities of a multi-element holographic scanner disc are made by optically replicating a silver halide master disc one element at a time in a dichromated gelatin film.
The dichromated gelatin film swells during pro-cessing. The swell is monitored during production by determining the shift in the angle of the Bragg surfaces within the gel. The angle of the repli-cating beam for each element is changed from that of the original reference beam to establish a Bragg angle at exposure which will be tilted to the pro-per angle after swelling in order to maximize the diffraction efficiency of the element at the original reference beam angle.
Description
S~S
METHOD FOR MAKING HOLOGRAPHIC OPTICAL
ELEMENTS WITH ~IGH ~IFFRACTION
EFFICIENCIES
Background of the Invention The present invention relates to optical scanners and more particularly to a method for making holographic optical elements with high difrraction efficiencies for use in such scanners.
One of the more significant changes which is occurring in retailing operations in general, and supermarket operations in particular, is the in-creasing use of optical scanners at customer checkout stations. Such scanners are used to read bar-coded labels which are printed on or affixed to product containers by producers or, in some instances, the store operator.
The bar-coded labels, the best known example of which is the UPC or Universal Product Code label, identify the product and permit the retrieval of product descriptors and prices from a system memory.
The product descriptors and prices are used to ~5 prepare descriptive customer receipt tapes and to compile transaction totals. The advantages of optical scanners are well known. Since individual containers no longer need be marked, less labor is s required to stock and maintain store shelf inven-tories. Optical scanners can also be used to sim-plify inventory control, to reduce the chances of operator mis-rings and to improve operator productivity.
~ lost currently available scanners use ro-tating mirrored drums or oscillating mirrors to deflect a laser beam onto a stationary set of mirrors which fold the beam along different paths to generate a label-scanning pattern. In re-cently introduced scanners, the rotating mirrored drums or oscillating mirrors may be replaced ~y holographic scanner discs. Such discs may in-clude a circumferential array of several holo-graphic optical elements. Each element is a photo-sensitive film which is a record of an interference pattern originally generated by exposing the film to two overlapping laser beams. Discs made up ~ of circumferential arrays of such elements are potentially much less costly than rotating mirrored drums or oscillating mirror mechanisms, and make it possible to focus scanning beams at different distances.
~;
One available process for making production ~uantities of multi-element holographic discs requires that a limited number of master discs be prepared. A greater number of copy discs are replicated from each master disc. The master discs are typically made using a sllver halide recording material. ~n interference pattern is recorded in each element of the master disc by interfering a collimated reference beam and a diverging image beam. The angles of the reference beam and image beam are fixed in advance by scanner ~ 7JS'~5 requirements but are identical to those ~hich are to exist when a copy of the master disc is used in an operating scanner. That is, the angle of the reference beam used in making a master element is the same as the angle of the reconstruction beam which illuminates the copy in an operating scanner. The angle of the image beam used in making a master elemen-t is the same angle at which the reconstructed or output beam leaves the corres-ponding element in a copy in an operating scanner.
When an element in a master disc is formed by interfering the two beams, a series of Bragg surfaces are formed within the recording material.
1~ The Bragg surfaces are parallel reflective quasi-planes which extend at an angle generally known as the Bragg angle, to the element surface. The spacing between the planes at the surface of the element is fixed at a distance d in accordance ~0 with the grating equation ~ = d (Sin aR - Sin 90) Eq. (1) where ~ is the wavelength of the coherent light ~5 beams, d is the spacing between adjacent Bragg planes measured along the surface of the recording material, ~R is the angle of the reference beam rela-tive to a normal to the recording medium surface, and ao is the angle of the image beam relative to the normal.
3~ Production quantities of the holographic op-tical elements are made by placing an unexposed piece of copy material closely adjacent a developed master holographic element and by illuminating the 75~5 ~981018 4 master element with a coherent light beam. When the beam passes through the master element, a part of it is diffracted or bent while the remainder remains undiffracted, passing straight through ; the element. The diffracted/undiffracted components of the beam interfere in the copy material to form an interference pattern in that material. The interference pattern is fi~ed or made permanent by processing the copy material. When the pro-cessed copy is illuminated with the coherent light beam, the replicated interference pattern is capable of reconstructing the image beam used in generating the master element.
1~ The recording material used in making the master element and the copy elements may be iden-tical. Similarly, the wavelength of the coherent light beams used in making the master elements and copy elements may also be the same. Preferably, however, the master elements are made by illumi-nating silver halide films with a laser beam having a wavelength in the red range. The interference pattern which is recorded in the silver halide material is ~ixed by largely conventional photo-graphic processing techniques. The copy material may be a dichromated gelatin material, which is not sensitive to red light. For this reason, the copying is performed with a coherent light beam in the blue or blue-green range. An image is fixed in dichromated gelatin material by washing the material in a series of water and alcohol baths.
One characteristic of dichromated gelatin is that it swells during processing and retains some residual swell normal to the surface after pro-cessing and drying. As a result, the recorded Bragg planes become distorted or tilted relative to their orientation at the time of exposure.
~75~
R~981018 5 If the swelling is ignored and the copy is illu-minated with the conjugate of the original refer-ence beam (that is, a beam having the same cross-sectional configuration as the original beam, but being directed in the opposite direction) the copy would still refract part of the beam along the angle ~O. However, the diffraction efficiency of the element would be significantly reduced; that is, a greàter portion of the beam would pass straight through the element while a lesser portion would be bent along the angle ~O. For reasons of scanner performance, it is important that the diffraction efficiency of each copy element be made as high as possible.
Attempts have been made to overcome the problem of reduced diffraction efficiencies due ~o swell by eliminating the residual gelatin swell through a series of chemical soaking steps. These ~0 attempts have only been marginally successful since swelling cannot be completely eliminated. Moreover, the steps are hard to control and the results have been erratic.
~5 Other attempts have been made to solve the problem by changing the angle of the reference beam which is used in making a master to compen-sate for the Bragg angle tilt resulting from the swelling. Unfortunately, this approach causes distortion of the output beam which is undesirable since it may impact the pexformance of the scanner.
Summary of the Invention The present invention is a method of making holographic optical elements with high diffraction efficiencies and low beam distortion characteristics.
An interference pattern previously recorded on a ~75~5 master element is optically replicated onto a closely adjacent, unexposed copy element made of a material which is known to change in thickness as a result of its post-exposure processing. The interference pattern recorded in the master ele-ment consists of parallel Bragg surfaces oriented at a desired angle relative to the master element surface. The method is characterized by the steps of illuminating the master element with a coherent replicating beam which is at an angle which establishes Bragg surfaces within the copy material at an intermediate angle relative to the copy material surface. The intermediate angle is different from the desired final angle of the lS Bragg surfaces. The copy material is then pro-cessed to fix the Bragg surfaces. The residual post-processing swell tilts the Bragg surfaces to the desired final angle.
Brief Description of the Drawings While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, de-tails of one embodiment of the invention may be more readily ascertained from the following de-tailed description when read in conjunction with the accompanying drawings wherein:
Figure 1 is an optical schematic diagram of the beam configurations and shapes used in generating a master element;
Figure 2 is an optical schematic diagram of the beam paths during the step of copying the master element;
~ ~5~!~5 ~A981018 7 Figure 3 is an optical schematic diagram of the beam paths during the use of a copy element to recon-struct an image beam;
Figure 4 is a representation of a cross section of copy material showing the effects of material swell on the angle of the Bragg surfaces within the material;
Figure 5 is a simplified cross section of re-cording material tha~ is used to define a number of terms: and Figure 6 is a perspective view of an appara-tus which can be used to monitor material swell through non-destructive measurements performed on finished discs.
Detailed Description Referring to Figure 1, production quantities of holographic optical elements are made by a process which starts'with the preparation of a master element. A photosensitive film, such as a silver halide photographic emulsion, is exposed to a coherent reference beam 10 and a coherent image beam 12, both of which are derived from a single coherent light source through conventional beam splitters and mirrors. Preferably, the reference beam 10 is collimated while the image beam 12 di-verges from a point source 14. Point source 14 may be a pin hole in the path of the beam 12.
The beams 10 and 12 overlap or interfere in region 16 of the photosensitive emulsion 18 to create a fringe pattern within the film. The pattern takes the form of parallel reflective or Bragg surfaces having an orientation which depends s upon the angle ~R of the reference beam and the angle ~o of the image beam as measured along nor-mals to the emulsion surface. Where the emulsion is a silver halide photographic emulsion, the in-terference pattern can be fixed or made permanent by conventional photographic development processes.
Referring to Figure 2, the master element 18 can be used to prepare a copy element 20 capable of reconstructing the image beam 12. An unexposed sheet of photosensitive copy material is placed closely adjacent the developed master element 18.
The master element 18 is illuminated with a repli-cating beam which is a collimated, coherent light beam 22, that impinges on the master element at an angle ~X. ~hen the beam 22 passes through the master element lg, separates into a diffracted or first order component 24 and an undiffracted or 0 order component 26. For reasons which will be explained in more detail later, the angle of incidence ~ of the replicating beam and the angle of departure ~Y of the diffracted beam 24 are not equal to the angles 3R and 90 of the original reference and image beams, respectively.
The 0 order beams 26 and the first order beam 24 interfere in the photosensitive copy material 20 to create a fringe pattern in that copy matexial.
When a dichromated gelatin film is employed, the replicated fringe pattern is amplified and fixed by a series of alcohol and water baths.
There is a certain amount of residual swell which cannot be eliminated, even after drying. As will be explained in more detail, the amount of resi~
dual swell is taken into account in establishing the appropriate angle of incidence 9X for the 3L~75~
replicating beam. The angle ~X also takes into account any difference in wavelengths of -the repli-cating beam used to make the copy element and the reference and image beams used to create the master element.
Referring to Figure 3, the copy element 20 can be used to reconstruct a beam 28 whlch is the conju-gate image of beam 12 used in making the master element 18. Beam 28 will have an angle of departure ~0 equal to the angle of incidence of beam 12 and will converge to a focal point 30 located at the same distance from copy element 20 as point source 14 was located from the master element 18. seam 28 is generated by illuminating the copy element 20 with a collimated reconstructing beam 32 which is the conjugate of the original reference beam 10.
Beam 32 illuminates the copy element 20 at an angle of incidence 3R equal to the angle of incidence of ~0 the original reference beam. Beam 32 is, however, directed along a path 180 from the path of the original reference beam. The coherent light source or laser which produces the reconstructing beam 32 operates at the same wavelength as the ~5 laser used to generate the original reference and image beams 10 and 12, respectively.
Figure 4 illustrates the effects of gelatin swell on Bragg planes shown in a greatly enlarged cross section of a portion of the copy film 20.
At the time of exposure, the copy material has a thickness t and Bragg planes which are at a given angle ~0 relative to a normal to the film surface.
In practice, the thic~ness t of the film is on the order of a few microns. The Bragg surfaces or planes formed within the material extend between opposite surfaces and have a surface spacing d ~5~65 which is fixed in accordance with the grating equation (1) men~ioned earlier when the master element is initially made. When the film swells as a result of processing, its thickness is in-creased by an incremental amount ~t. Since the spacing d between the Bragg surfaces remains fixed, the effect of swell is to tilt or realign the Bragg planes at an angle aSW relative to a normal to the film surface. The difference be-tween ~SW and ~0 is referred to as ~a.
aSW should be equal to the Bragg angle or ~ of the planes which are established when the silver halide master element is made. To establish an ~SW
at the proper value, an intermediate a 0 must be established at the time of exposure of the copy element so that the Bragg planes will be tilted to the proper aSW as a result of gelatin swell.
The determination of the proper angle aO requires knowledge of both the amount of swell and the wavelength of the replicating beam.
Referring to Figure S, the appropriate Bragg plane angle ~O is established in the copy material ~5 at the time of exposure by varying the angle of the replicating beam. Figure 5 defines a number of terms which will be used in explaining how the appro-priate replicating beam angle is determined. ~X and 9Y are the angle of incidence and the angle of de-parture of a light beam incident on the film surface.
9X' is the angle of the incident beam relative to a normal within the film material. ~Y' is the angle of departure within the material. ~X and ~X' are different where the index of refraction of the film material is not equal to the index of refrac-tion of the medium through which the beam travels before reaching the film. 3Y' and aY are different for the same reasons. The terms d and a have been defined previously.
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In preparing a final copy element, the objective is to establish sragg planes which would yield an output beam at an angle ~0 at a maximum diffraction efficiency for a given reference beam angle ~R.
The angles OR and ~0 are the angles of incidences of the reference beam and image beam used in pre-paring the master element. These angles are fixed by scanner requirements. The Bragg angle 9SW in the final copy disc must satisfy the Bragg equation gy~ - 3X = aSW Eq. (2) where the angles ~Y' and ~X' are measured within the 1~ copy material.
The angle of incidence of the beam ~X which will produce the internal beam 9X' can be determined from Snell's equation which can be stated as nl sin ~1 = n2 sin ~2 Eq. (3) where nl and n2 are the indices of refraction of two adjacent materials (such as air and glass or ~5 glass and gelatin) while 31 and ~2 are the angles of a light beam transmitted through those mediums.
Where nl and n2 are different, a light beam which is transmitted from one medium to the other will be refracted or bent at the interface between the two mediums.
To find aO given aSW, knowledge of the spacing d between adjacent Bragg surfaces is required along with knowledge of the relative change in thickness of the gel as a result of processing. An analysis of the geometry of the gel shows the tangent ~SW
equals d/(t + Qt) while tangent aO equals d/t. There-fore, (tangent aSW) x (t + Qt) equals (tangent aO) x (t).
~ ~5~S
For small angles, the tangent of an angle is approxi-mately equal to the value o~ the angle itself in radians. Therefore, aSW X [ (t) plus (~t)] equals ~0 x (t). Solving this equation for ~0, it can be found that ~0 = ~SW (1 + ~t) Eq. (4) Once ~0 has been calculated in accordance with this equatlon, ~X' and ~Y' can be calculated by simul-taneously solving the following two equations sin ~Y' - sin ~X' Eq. (5) ~0 = aY -2 ~X Eq. (6) where ~X' is the angle of the replicating beam within the gel at the time of exposure, aY' is the angle of departure of the replicating beam with-in the gel at the time of exposure, ~ is the wave-length of the replicating beam, and d is the surface spacing between adjacent Bragg surfaces.
Once 3X' and ~Y' have been calculated, the ~5 appropriate angle of incidence 9X for the repli-cating beam outside of the gel can be calculated through the use of the following equation where nl represents the index of refraction of air and n2 represents the index of refraction of the gel.
~X = sin 1 (nl sin 3X') Eq. (7) If Bragg planes at an angle ~0 are established in the copy material at the time of exposure, the swell of that material will tilt those Bragg planes to the angle ~SW. When the copy material is illu-minated with a reconstructing beam at an angle of incidence 3R, the output beam will leave the element at an angle ~O at maximum diffraction efficiency.
~ 75~2ÇiS
Clearly, calculation of ~X require knowledge of the relative amount of swell that can be ex-pected when the copy material is processed. In accordance with this invention, the relative amount of swell is determined by means of op-tical measurements which are performed on pre-viously produced multi-element holographic discs by means of an arrangement illustrated in Figure 6.
A finished disc may include on the order of 20 facets or holographic optical elements in an annular film of dichromated gelatin materialO
The film is sandwiched between two clear glass substrates. The finished disc 34 is mounted on a vertical post 36 located at the center of a graduated rotating table 38. Such a table is marked in degrees or radians and can provide a direct indication through a table angle readout mechanism 40 of the angle of the mounted disc relati~e to a laser 42.
In use, the position of the rotating table 38 is adjusted so that an output beam 44 from laser 42 strikes the disc surface at a normal, ~5 which is indicated when the laser beam i5 re-flected back along its own path. At this point, the table readout would be reset or recalibrated to orovide a 0 reading. A photodetector 46 is placed in the path of the diffracted or first order beam 48 produced when the laser beam is transmitted through an element 50 on the disc.
The element 50 being investigated has its sragg planes lying in planes parallel to the axis about which the disc is rotated; namely, the axis of the post 36. It should be noted that post 36 is offset from the center of the disc.
It is coincident with the center of the element 5;265 RA981018 1~
being illuminated; namely, element 50. The outpuL of the photodetector 46 is applied to an indicator such as a vol-tmeter 52.
The table 38 is rotated about the axis of post 36 until the voltmeter reading is maximized, indicating that beam 48 is being produced wi-th maximum diffraction efficiency. The angle through which the table 38 has been rotated is the angle of incidence for which maximum diffrac~
tion efficiency actually occurs.
An alternate technique for establishing the angle ~R which produces ~o at maximum diffraction efficiency requires that the maximum voltmeter reading first be noted. The approximate angle at which maximum voltmeter reading occurs is also noted. The rotating table is moved in one di-rection until the voltmeter reading is 90% of the noted peak value. The first angle 9Rl at which the 90% peak reading occurs is noted. The rotating table is then moved through the peak reading area until a second angle ~R2 is en-countered which produces a voltmeter reading at ~5 90% peak value. The average of 3Rl and 9R2 is the angle aR at which maximum diffraction effi ciency occurs.
Using the grating equation (1) and knowing the angle of incidence, the spacing d for the element ;0 and the wavelength ~ for laser 42, the angle of departure of the diffracted beam 48 can be calculated.
When angles of incidence and departure have been calculated, the Bragg equation can be used to determine the actual SW for the element 50.
~s~
As noted earlier, SW is nominally equal to the sragg angle a established when the master element is made.
The Bragg angle ~0 at the time of exposure can be calculated for the element 50 using the Bragg equation and the grating equation since the actual angle of incidence of the replicating beam for element 50 will be known.
When aSW has been found and aO has been calcu-lated, the following equation can be used to cal-culate the relative change in thickness or the amount of residual swell of gelatin material as a result of processing:
t aSW 1 Eq. (8) This equation is derived simply b~ rearranging the terms of equation (4).
~0 If the amount of gelatin swell is not changed significantly, no corrections need be made in the angle of the replicating beam. If, however, the amount of swell deviates, the angle of incidence of the replicating beam can be adjusted to produce an aO which will result in the desired aSW in subsequently produced elements.
While there has been described what is con-sidered to be a preferred embodiment of the inven-tion, variations and modifications therein will occur to those skilled in the art once they be-come familiar with the basic concepts of the inven-tion. Therefore, it is intended that the appended claims shall be construed to include all such variations and modifications as fall within the true spirit and scope of the invention.
METHOD FOR MAKING HOLOGRAPHIC OPTICAL
ELEMENTS WITH ~IGH ~IFFRACTION
EFFICIENCIES
Background of the Invention The present invention relates to optical scanners and more particularly to a method for making holographic optical elements with high difrraction efficiencies for use in such scanners.
One of the more significant changes which is occurring in retailing operations in general, and supermarket operations in particular, is the in-creasing use of optical scanners at customer checkout stations. Such scanners are used to read bar-coded labels which are printed on or affixed to product containers by producers or, in some instances, the store operator.
The bar-coded labels, the best known example of which is the UPC or Universal Product Code label, identify the product and permit the retrieval of product descriptors and prices from a system memory.
The product descriptors and prices are used to ~5 prepare descriptive customer receipt tapes and to compile transaction totals. The advantages of optical scanners are well known. Since individual containers no longer need be marked, less labor is s required to stock and maintain store shelf inven-tories. Optical scanners can also be used to sim-plify inventory control, to reduce the chances of operator mis-rings and to improve operator productivity.
~ lost currently available scanners use ro-tating mirrored drums or oscillating mirrors to deflect a laser beam onto a stationary set of mirrors which fold the beam along different paths to generate a label-scanning pattern. In re-cently introduced scanners, the rotating mirrored drums or oscillating mirrors may be replaced ~y holographic scanner discs. Such discs may in-clude a circumferential array of several holo-graphic optical elements. Each element is a photo-sensitive film which is a record of an interference pattern originally generated by exposing the film to two overlapping laser beams. Discs made up ~ of circumferential arrays of such elements are potentially much less costly than rotating mirrored drums or oscillating mirror mechanisms, and make it possible to focus scanning beams at different distances.
~;
One available process for making production ~uantities of multi-element holographic discs requires that a limited number of master discs be prepared. A greater number of copy discs are replicated from each master disc. The master discs are typically made using a sllver halide recording material. ~n interference pattern is recorded in each element of the master disc by interfering a collimated reference beam and a diverging image beam. The angles of the reference beam and image beam are fixed in advance by scanner ~ 7JS'~5 requirements but are identical to those ~hich are to exist when a copy of the master disc is used in an operating scanner. That is, the angle of the reference beam used in making a master element is the same as the angle of the reconstruction beam which illuminates the copy in an operating scanner. The angle of the image beam used in making a master elemen-t is the same angle at which the reconstructed or output beam leaves the corres-ponding element in a copy in an operating scanner.
When an element in a master disc is formed by interfering the two beams, a series of Bragg surfaces are formed within the recording material.
1~ The Bragg surfaces are parallel reflective quasi-planes which extend at an angle generally known as the Bragg angle, to the element surface. The spacing between the planes at the surface of the element is fixed at a distance d in accordance ~0 with the grating equation ~ = d (Sin aR - Sin 90) Eq. (1) where ~ is the wavelength of the coherent light ~5 beams, d is the spacing between adjacent Bragg planes measured along the surface of the recording material, ~R is the angle of the reference beam rela-tive to a normal to the recording medium surface, and ao is the angle of the image beam relative to the normal.
3~ Production quantities of the holographic op-tical elements are made by placing an unexposed piece of copy material closely adjacent a developed master holographic element and by illuminating the 75~5 ~981018 4 master element with a coherent light beam. When the beam passes through the master element, a part of it is diffracted or bent while the remainder remains undiffracted, passing straight through ; the element. The diffracted/undiffracted components of the beam interfere in the copy material to form an interference pattern in that material. The interference pattern is fi~ed or made permanent by processing the copy material. When the pro-cessed copy is illuminated with the coherent light beam, the replicated interference pattern is capable of reconstructing the image beam used in generating the master element.
1~ The recording material used in making the master element and the copy elements may be iden-tical. Similarly, the wavelength of the coherent light beams used in making the master elements and copy elements may also be the same. Preferably, however, the master elements are made by illumi-nating silver halide films with a laser beam having a wavelength in the red range. The interference pattern which is recorded in the silver halide material is ~ixed by largely conventional photo-graphic processing techniques. The copy material may be a dichromated gelatin material, which is not sensitive to red light. For this reason, the copying is performed with a coherent light beam in the blue or blue-green range. An image is fixed in dichromated gelatin material by washing the material in a series of water and alcohol baths.
One characteristic of dichromated gelatin is that it swells during processing and retains some residual swell normal to the surface after pro-cessing and drying. As a result, the recorded Bragg planes become distorted or tilted relative to their orientation at the time of exposure.
~75~
R~981018 5 If the swelling is ignored and the copy is illu-minated with the conjugate of the original refer-ence beam (that is, a beam having the same cross-sectional configuration as the original beam, but being directed in the opposite direction) the copy would still refract part of the beam along the angle ~O. However, the diffraction efficiency of the element would be significantly reduced; that is, a greàter portion of the beam would pass straight through the element while a lesser portion would be bent along the angle ~O. For reasons of scanner performance, it is important that the diffraction efficiency of each copy element be made as high as possible.
Attempts have been made to overcome the problem of reduced diffraction efficiencies due ~o swell by eliminating the residual gelatin swell through a series of chemical soaking steps. These ~0 attempts have only been marginally successful since swelling cannot be completely eliminated. Moreover, the steps are hard to control and the results have been erratic.
~5 Other attempts have been made to solve the problem by changing the angle of the reference beam which is used in making a master to compen-sate for the Bragg angle tilt resulting from the swelling. Unfortunately, this approach causes distortion of the output beam which is undesirable since it may impact the pexformance of the scanner.
Summary of the Invention The present invention is a method of making holographic optical elements with high diffraction efficiencies and low beam distortion characteristics.
An interference pattern previously recorded on a ~75~5 master element is optically replicated onto a closely adjacent, unexposed copy element made of a material which is known to change in thickness as a result of its post-exposure processing. The interference pattern recorded in the master ele-ment consists of parallel Bragg surfaces oriented at a desired angle relative to the master element surface. The method is characterized by the steps of illuminating the master element with a coherent replicating beam which is at an angle which establishes Bragg surfaces within the copy material at an intermediate angle relative to the copy material surface. The intermediate angle is different from the desired final angle of the lS Bragg surfaces. The copy material is then pro-cessed to fix the Bragg surfaces. The residual post-processing swell tilts the Bragg surfaces to the desired final angle.
Brief Description of the Drawings While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, de-tails of one embodiment of the invention may be more readily ascertained from the following de-tailed description when read in conjunction with the accompanying drawings wherein:
Figure 1 is an optical schematic diagram of the beam configurations and shapes used in generating a master element;
Figure 2 is an optical schematic diagram of the beam paths during the step of copying the master element;
~ ~5~!~5 ~A981018 7 Figure 3 is an optical schematic diagram of the beam paths during the use of a copy element to recon-struct an image beam;
Figure 4 is a representation of a cross section of copy material showing the effects of material swell on the angle of the Bragg surfaces within the material;
Figure 5 is a simplified cross section of re-cording material tha~ is used to define a number of terms: and Figure 6 is a perspective view of an appara-tus which can be used to monitor material swell through non-destructive measurements performed on finished discs.
Detailed Description Referring to Figure 1, production quantities of holographic optical elements are made by a process which starts'with the preparation of a master element. A photosensitive film, such as a silver halide photographic emulsion, is exposed to a coherent reference beam 10 and a coherent image beam 12, both of which are derived from a single coherent light source through conventional beam splitters and mirrors. Preferably, the reference beam 10 is collimated while the image beam 12 di-verges from a point source 14. Point source 14 may be a pin hole in the path of the beam 12.
The beams 10 and 12 overlap or interfere in region 16 of the photosensitive emulsion 18 to create a fringe pattern within the film. The pattern takes the form of parallel reflective or Bragg surfaces having an orientation which depends s upon the angle ~R of the reference beam and the angle ~o of the image beam as measured along nor-mals to the emulsion surface. Where the emulsion is a silver halide photographic emulsion, the in-terference pattern can be fixed or made permanent by conventional photographic development processes.
Referring to Figure 2, the master element 18 can be used to prepare a copy element 20 capable of reconstructing the image beam 12. An unexposed sheet of photosensitive copy material is placed closely adjacent the developed master element 18.
The master element 18 is illuminated with a repli-cating beam which is a collimated, coherent light beam 22, that impinges on the master element at an angle ~X. ~hen the beam 22 passes through the master element lg, separates into a diffracted or first order component 24 and an undiffracted or 0 order component 26. For reasons which will be explained in more detail later, the angle of incidence ~ of the replicating beam and the angle of departure ~Y of the diffracted beam 24 are not equal to the angles 3R and 90 of the original reference and image beams, respectively.
The 0 order beams 26 and the first order beam 24 interfere in the photosensitive copy material 20 to create a fringe pattern in that copy matexial.
When a dichromated gelatin film is employed, the replicated fringe pattern is amplified and fixed by a series of alcohol and water baths.
There is a certain amount of residual swell which cannot be eliminated, even after drying. As will be explained in more detail, the amount of resi~
dual swell is taken into account in establishing the appropriate angle of incidence 9X for the 3L~75~
replicating beam. The angle ~X also takes into account any difference in wavelengths of -the repli-cating beam used to make the copy element and the reference and image beams used to create the master element.
Referring to Figure 3, the copy element 20 can be used to reconstruct a beam 28 whlch is the conju-gate image of beam 12 used in making the master element 18. Beam 28 will have an angle of departure ~0 equal to the angle of incidence of beam 12 and will converge to a focal point 30 located at the same distance from copy element 20 as point source 14 was located from the master element 18. seam 28 is generated by illuminating the copy element 20 with a collimated reconstructing beam 32 which is the conjugate of the original reference beam 10.
Beam 32 illuminates the copy element 20 at an angle of incidence 3R equal to the angle of incidence of ~0 the original reference beam. Beam 32 is, however, directed along a path 180 from the path of the original reference beam. The coherent light source or laser which produces the reconstructing beam 32 operates at the same wavelength as the ~5 laser used to generate the original reference and image beams 10 and 12, respectively.
Figure 4 illustrates the effects of gelatin swell on Bragg planes shown in a greatly enlarged cross section of a portion of the copy film 20.
At the time of exposure, the copy material has a thickness t and Bragg planes which are at a given angle ~0 relative to a normal to the film surface.
In practice, the thic~ness t of the film is on the order of a few microns. The Bragg surfaces or planes formed within the material extend between opposite surfaces and have a surface spacing d ~5~65 which is fixed in accordance with the grating equation (1) men~ioned earlier when the master element is initially made. When the film swells as a result of processing, its thickness is in-creased by an incremental amount ~t. Since the spacing d between the Bragg surfaces remains fixed, the effect of swell is to tilt or realign the Bragg planes at an angle aSW relative to a normal to the film surface. The difference be-tween ~SW and ~0 is referred to as ~a.
aSW should be equal to the Bragg angle or ~ of the planes which are established when the silver halide master element is made. To establish an ~SW
at the proper value, an intermediate a 0 must be established at the time of exposure of the copy element so that the Bragg planes will be tilted to the proper aSW as a result of gelatin swell.
The determination of the proper angle aO requires knowledge of both the amount of swell and the wavelength of the replicating beam.
Referring to Figure S, the appropriate Bragg plane angle ~O is established in the copy material ~5 at the time of exposure by varying the angle of the replicating beam. Figure 5 defines a number of terms which will be used in explaining how the appro-priate replicating beam angle is determined. ~X and 9Y are the angle of incidence and the angle of de-parture of a light beam incident on the film surface.
9X' is the angle of the incident beam relative to a normal within the film material. ~Y' is the angle of departure within the material. ~X and ~X' are different where the index of refraction of the film material is not equal to the index of refrac-tion of the medium through which the beam travels before reaching the film. 3Y' and aY are different for the same reasons. The terms d and a have been defined previously.
~75~
In preparing a final copy element, the objective is to establish sragg planes which would yield an output beam at an angle ~0 at a maximum diffraction efficiency for a given reference beam angle ~R.
The angles OR and ~0 are the angles of incidences of the reference beam and image beam used in pre-paring the master element. These angles are fixed by scanner requirements. The Bragg angle 9SW in the final copy disc must satisfy the Bragg equation gy~ - 3X = aSW Eq. (2) where the angles ~Y' and ~X' are measured within the 1~ copy material.
The angle of incidence of the beam ~X which will produce the internal beam 9X' can be determined from Snell's equation which can be stated as nl sin ~1 = n2 sin ~2 Eq. (3) where nl and n2 are the indices of refraction of two adjacent materials (such as air and glass or ~5 glass and gelatin) while 31 and ~2 are the angles of a light beam transmitted through those mediums.
Where nl and n2 are different, a light beam which is transmitted from one medium to the other will be refracted or bent at the interface between the two mediums.
To find aO given aSW, knowledge of the spacing d between adjacent Bragg surfaces is required along with knowledge of the relative change in thickness of the gel as a result of processing. An analysis of the geometry of the gel shows the tangent ~SW
equals d/(t + Qt) while tangent aO equals d/t. There-fore, (tangent aSW) x (t + Qt) equals (tangent aO) x (t).
~ ~5~S
For small angles, the tangent of an angle is approxi-mately equal to the value o~ the angle itself in radians. Therefore, aSW X [ (t) plus (~t)] equals ~0 x (t). Solving this equation for ~0, it can be found that ~0 = ~SW (1 + ~t) Eq. (4) Once ~0 has been calculated in accordance with this equatlon, ~X' and ~Y' can be calculated by simul-taneously solving the following two equations sin ~Y' - sin ~X' Eq. (5) ~0 = aY -2 ~X Eq. (6) where ~X' is the angle of the replicating beam within the gel at the time of exposure, aY' is the angle of departure of the replicating beam with-in the gel at the time of exposure, ~ is the wave-length of the replicating beam, and d is the surface spacing between adjacent Bragg surfaces.
Once 3X' and ~Y' have been calculated, the ~5 appropriate angle of incidence 9X for the repli-cating beam outside of the gel can be calculated through the use of the following equation where nl represents the index of refraction of air and n2 represents the index of refraction of the gel.
~X = sin 1 (nl sin 3X') Eq. (7) If Bragg planes at an angle ~0 are established in the copy material at the time of exposure, the swell of that material will tilt those Bragg planes to the angle ~SW. When the copy material is illu-minated with a reconstructing beam at an angle of incidence 3R, the output beam will leave the element at an angle ~O at maximum diffraction efficiency.
~ 75~2ÇiS
Clearly, calculation of ~X require knowledge of the relative amount of swell that can be ex-pected when the copy material is processed. In accordance with this invention, the relative amount of swell is determined by means of op-tical measurements which are performed on pre-viously produced multi-element holographic discs by means of an arrangement illustrated in Figure 6.
A finished disc may include on the order of 20 facets or holographic optical elements in an annular film of dichromated gelatin materialO
The film is sandwiched between two clear glass substrates. The finished disc 34 is mounted on a vertical post 36 located at the center of a graduated rotating table 38. Such a table is marked in degrees or radians and can provide a direct indication through a table angle readout mechanism 40 of the angle of the mounted disc relati~e to a laser 42.
In use, the position of the rotating table 38 is adjusted so that an output beam 44 from laser 42 strikes the disc surface at a normal, ~5 which is indicated when the laser beam i5 re-flected back along its own path. At this point, the table readout would be reset or recalibrated to orovide a 0 reading. A photodetector 46 is placed in the path of the diffracted or first order beam 48 produced when the laser beam is transmitted through an element 50 on the disc.
The element 50 being investigated has its sragg planes lying in planes parallel to the axis about which the disc is rotated; namely, the axis of the post 36. It should be noted that post 36 is offset from the center of the disc.
It is coincident with the center of the element 5;265 RA981018 1~
being illuminated; namely, element 50. The outpuL of the photodetector 46 is applied to an indicator such as a vol-tmeter 52.
The table 38 is rotated about the axis of post 36 until the voltmeter reading is maximized, indicating that beam 48 is being produced wi-th maximum diffraction efficiency. The angle through which the table 38 has been rotated is the angle of incidence for which maximum diffrac~
tion efficiency actually occurs.
An alternate technique for establishing the angle ~R which produces ~o at maximum diffraction efficiency requires that the maximum voltmeter reading first be noted. The approximate angle at which maximum voltmeter reading occurs is also noted. The rotating table is moved in one di-rection until the voltmeter reading is 90% of the noted peak value. The first angle 9Rl at which the 90% peak reading occurs is noted. The rotating table is then moved through the peak reading area until a second angle ~R2 is en-countered which produces a voltmeter reading at ~5 90% peak value. The average of 3Rl and 9R2 is the angle aR at which maximum diffraction effi ciency occurs.
Using the grating equation (1) and knowing the angle of incidence, the spacing d for the element ;0 and the wavelength ~ for laser 42, the angle of departure of the diffracted beam 48 can be calculated.
When angles of incidence and departure have been calculated, the Bragg equation can be used to determine the actual SW for the element 50.
~s~
As noted earlier, SW is nominally equal to the sragg angle a established when the master element is made.
The Bragg angle ~0 at the time of exposure can be calculated for the element 50 using the Bragg equation and the grating equation since the actual angle of incidence of the replicating beam for element 50 will be known.
When aSW has been found and aO has been calcu-lated, the following equation can be used to cal-culate the relative change in thickness or the amount of residual swell of gelatin material as a result of processing:
t aSW 1 Eq. (8) This equation is derived simply b~ rearranging the terms of equation (4).
~0 If the amount of gelatin swell is not changed significantly, no corrections need be made in the angle of the replicating beam. If, however, the amount of swell deviates, the angle of incidence of the replicating beam can be adjusted to produce an aO which will result in the desired aSW in subsequently produced elements.
While there has been described what is con-sidered to be a preferred embodiment of the inven-tion, variations and modifications therein will occur to those skilled in the art once they be-come familiar with the basic concepts of the inven-tion. Therefore, it is intended that the appended claims shall be construed to include all such variations and modifications as fall within the true spirit and scope of the invention.
Claims (4)
1. A method of making holographic optical elements with high diffraction efficiencies by optically repli-cating a previously recorded interference pattern from a master element onto a closely adjacent, unexposed copy element which is known to change in thickness as a re-sult of post-exposure processing, said interference pattern consisting of parallel Bragg surfaces within the master element oriented at a desired angle relative to the master element surface, said method being charac-terized by the steps of:
illuminating the master element with a coherent replicating beam oriented to initially establish Bragg surfaces within the closely adjacent copy material at an intermediate angle relative to the copy material surface, said intermediate angle being different from the desired final angle of the Bragg surfaces in the copy; and processing the copy material to fix the Bragg surfaces, said Bragg surfaces being tilted to the desired final angle as a result of process-induced changes in the thickness of the copy material.
illuminating the master element with a coherent replicating beam oriented to initially establish Bragg surfaces within the closely adjacent copy material at an intermediate angle relative to the copy material surface, said intermediate angle being different from the desired final angle of the Bragg surfaces in the copy; and processing the copy material to fix the Bragg surfaces, said Bragg surfaces being tilted to the desired final angle as a result of process-induced changes in the thickness of the copy material.
2. A method as defined in Claim 1 wherein the orientation of the replicating beam is also a function of the wavelength of that beam.
3. A method as defined in Claim 1 characterized by the additional steps of monitoring the process induced changes in thickness of previously produced copy elements and adjusting the orientation of the replicating beam to reflect any thickness changes not previously taken into account.
4. A method as defined in Claim 3 wherein the steps of monitoring thickness further comprise:
establishing the spacing d and the angle .alpha.0 of the Bragg surfaces in the copy material at the time of exposure;
illuminating the copy element after processing with a coherent light beam having a known wavelength .lambda.;
rotating the element about an axis parallel to the plane of the Bragg surfaces and perpendicular to the axis of the coherent light beam while measuring the intensity of the diffracted beam to determine the angle of incidence .theta.R at which maximum diffraction effi-ciency occurs;
determining the angle .alpha.SW of the Bragg surfaces in the processed element as a function of .lambda., d and the determined angle of incidence .theta.R; and determining the relative change in thickness as a function of the relative values of the angles .alpha.0 and .alpha.SW.
establishing the spacing d and the angle .alpha.0 of the Bragg surfaces in the copy material at the time of exposure;
illuminating the copy element after processing with a coherent light beam having a known wavelength .lambda.;
rotating the element about an axis parallel to the plane of the Bragg surfaces and perpendicular to the axis of the coherent light beam while measuring the intensity of the diffracted beam to determine the angle of incidence .theta.R at which maximum diffraction effi-ciency occurs;
determining the angle .alpha.SW of the Bragg surfaces in the processed element as a function of .lambda., d and the determined angle of incidence .theta.R; and determining the relative change in thickness as a function of the relative values of the angles .alpha.0 and .alpha.SW.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US314,645 | 1981-10-26 | ||
| US06/314,645 US4416505A (en) | 1981-10-26 | 1981-10-26 | Method for making holographic optical elements with high diffraction efficiencies |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175265A true CA1175265A (en) | 1984-10-02 |
Family
ID=23220827
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000411879A Expired CA1175265A (en) | 1981-10-26 | 1982-09-21 | Method for making holographic optical elements with high diffraction efficiencies |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4416505A (en) |
| EP (1) | EP0077925B1 (en) |
| JP (1) | JPS5880684A (en) |
| CA (1) | CA1175265A (en) |
| DE (1) | DE3272331D1 (en) |
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| CA1252321A (en) * | 1983-10-03 | 1989-04-11 | Hiroyuki Ikeda | Method for constructing and reconstructing hologram |
| JPS60108802A (en) * | 1983-11-18 | 1985-06-14 | Fuji Photo Film Co Ltd | Method and device for optical beam synthesis |
| US4752130A (en) * | 1986-10-24 | 1988-06-21 | The University Of Rochester | Optical systems utilizing a volume transmission diffraction element to provide wavelength tuning |
| GB2271435B (en) * | 1992-10-06 | 1996-05-22 | Grumman Aerospace Corp | A system and method of fabricating multiple holographic elements |
| US7051922B2 (en) | 1994-08-17 | 2006-05-30 | Metrologic Instruments, Inc. | Compact bioptical laser scanning system |
| US6006993A (en) * | 1994-08-17 | 1999-12-28 | Metrologic Instruments, Inc. | Holographic laser scanning system for carrying out laser beam scanning operations with improved scan angle multiplication efficiency and carrying out light collection operations with improved light collection efficiency |
| US6003772A (en) * | 1994-08-17 | 1999-12-21 | Metrologic Instruments, Inc. | Holographic laser scanning system employing holographic scanning disc having dual-fringe contrast regions for optimized laser beam scanning and light collection operations |
| US6085978A (en) * | 1994-08-17 | 2000-07-11 | Metrologic Instruments, Inc. | Holographic laser scanners of modular construction and method and apparatus for designing and manufacturing the same |
| US6758402B1 (en) * | 1994-08-17 | 2004-07-06 | Metrologic Instruments, Inc. | Bioptical holographic laser scanning system |
| US6547144B1 (en) | 1994-08-17 | 2003-04-15 | Metrologic Instruments, Inc. | Holographic laser scanning system for carrying out light collection operations with improved light collection efficiency |
| US6158659A (en) * | 1994-08-17 | 2000-12-12 | Metrologic Instruments, Inc. | Holographic laser scanning system having multiple laser scanning stations for producing a 3-D scanning volume substantially free of spatially and temporally coincident scanning planes |
| US6199759B1 (en) * | 1994-08-17 | 2001-03-13 | Metrologic Instruments, Inc. | Bar code symbol scanning system having a holographic laser scanning disc utilizing maximum light collection surface area thereof and having scanning facets with optimized light collection efficiency |
| US6073846A (en) | 1994-08-17 | 2000-06-13 | Metrologic Instruments, Inc. | Holographic laser scanning system and process and apparatus and method |
| US6619550B1 (en) | 1995-12-18 | 2003-09-16 | Metrologic Instruments, Inc. | Automated tunnel-type laser scanning system employing corner-projected orthogonal laser scanning patterns for enhanced reading of ladder and picket fence oriented bar codes on packages moving therethrough |
| US6629640B2 (en) * | 1995-12-18 | 2003-10-07 | Metrologic Instruments, Inc. | Holographic laser scanning method and system employing visible scanning-zone indicators identifying a three-dimensional omni-directional laser scanning volume for package transport navigation |
| US6100975A (en) * | 1996-05-13 | 2000-08-08 | Process Instruments, Inc. | Raman spectroscopy apparatus and method using external cavity laser for continuous chemical analysis of sample streams |
| US6028667A (en) * | 1996-05-13 | 2000-02-22 | Process Instruments, Inc. | Compact and robust spectrograph |
| US5751415A (en) * | 1996-05-13 | 1998-05-12 | Process Instruments, Inc. | Raman spectroscopy apparatus and method for continuous chemical analysis of fluid streams |
| US6097514A (en) * | 1996-07-31 | 2000-08-01 | Dai Nippon Printing Co., Ltd. | Hologram replicating method, and volume hologram |
| US6052209A (en) * | 1996-07-31 | 2000-04-18 | Dai Nippon Printing Co., Ltd. | Hologram reproduction process and volume hologram |
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| US6579673B2 (en) | 1998-12-17 | 2003-06-17 | Kimberly-Clark Worldwide, Inc. | Patterned deposition of antibody binding protein for optical diffraction-based biosensors |
| US6307662B1 (en) | 1999-01-21 | 2001-10-23 | Ncr Corporation | Blazed diffraction scanner |
| US7167615B1 (en) | 1999-11-05 | 2007-01-23 | Board Of Regents, The University Of Texas System | Resonant waveguide-grating filters and sensors and methods for making and using same |
| US6399295B1 (en) | 1999-12-17 | 2002-06-04 | Kimberly-Clark Worldwide, Inc. | Use of wicking agent to eliminate wash steps for optical diffraction-based biosensors |
| JP4330762B2 (en) | 2000-04-21 | 2009-09-16 | 富士フイルム株式会社 | Multi-beam exposure system |
| JP4608155B2 (en) * | 2001-09-28 | 2011-01-05 | 中洲電機株式会社 | Electrical connection screw |
| US7098041B2 (en) | 2001-12-11 | 2006-08-29 | Kimberly-Clark Worldwide, Inc. | Methods to view and analyze the results from diffraction-based diagnostics |
| US7102752B2 (en) * | 2001-12-11 | 2006-09-05 | Kimberly-Clark Worldwide, Inc. | Systems to view and analyze the results from diffraction-based diagnostics |
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| US7118855B2 (en) * | 2002-05-03 | 2006-10-10 | Kimberly-Clark Worldwide, Inc. | Diffraction-based diagnostic devices |
| US7223534B2 (en) | 2002-05-03 | 2007-05-29 | Kimberly-Clark Worldwide, Inc. | Diffraction-based diagnostic devices |
| US7214530B2 (en) * | 2002-05-03 | 2007-05-08 | Kimberly-Clark Worldwide, Inc. | Biomolecule diagnostic devices and method for producing biomolecule diagnostic devices |
| US7485453B2 (en) * | 2002-05-03 | 2009-02-03 | Kimberly-Clark Worldwide, Inc. | Diffraction-based diagnostic devices |
| US7091049B2 (en) | 2002-06-26 | 2006-08-15 | Kimberly-Clark Worldwide, Inc. | Enhanced diffraction-based biosensor devices |
| US7169550B2 (en) * | 2002-09-26 | 2007-01-30 | Kimberly-Clark Worldwide, Inc. | Diffraction-based diagnostic devices |
| KR101225561B1 (en) | 2010-09-07 | 2013-01-24 | 다이니폰 인사츠 가부시키가이샤 | Projection-type footage display device |
| CN103097857B (en) | 2010-09-07 | 2014-12-24 | 大日本印刷株式会社 | Scanner device and device for measuring three-dimensional shape of object |
| KR101987981B1 (en) | 2010-09-07 | 2019-06-11 | 다이니폰 인사츠 가부시키가이샤 | Optical module |
| US9442460B2 (en) * | 2012-10-31 | 2016-09-13 | Lg Display Co., Ltd. | Digital hologram display device |
| US9541900B2 (en) * | 2013-12-26 | 2017-01-10 | Lg Display Co., Ltd. | Method for producing a beam shaping holographic optical element |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5017132A (en) * | 1973-06-13 | 1975-02-22 | ||
| JPS5573079A (en) * | 1978-11-28 | 1980-06-02 | Fujitsu Ltd | Information recording-reproducing method |
-
1981
- 1981-10-26 US US06/314,645 patent/US4416505A/en not_active Expired - Fee Related
-
1982
- 1982-08-20 JP JP57143555A patent/JPS5880684A/en active Granted
- 1982-09-21 CA CA000411879A patent/CA1175265A/en not_active Expired
- 1982-09-22 DE DE8282108771T patent/DE3272331D1/en not_active Expired
- 1982-09-22 EP EP82108771A patent/EP0077925B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5880684A (en) | 1983-05-14 |
| US4416505A (en) | 1983-11-22 |
| EP0077925A1 (en) | 1983-05-04 |
| JPH0360116B2 (en) | 1991-09-12 |
| DE3272331D1 (en) | 1986-09-04 |
| EP0077925B1 (en) | 1986-07-30 |
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